1. Field of the Invention
The present invention relates to a personal watercraft (PWC) which ejects water rearward and planes on a water surface as the resulting reaction, and more particularly to a personal watercraft having a water cooling system of an engine.
2. Description of the Related Art
In recent years, personal watercraft have been widely used in leisure, sport, rescue activities, and the like. The personal watercraft has a straddle-type body structure, and is configured to have a water jet pump that pressurizes and accelerates water sucked from a water intake generally provided on a hull bottom surface and ejects it rearward from an outlet port. Thereby, the personal watercraft is propelled.
In general, the personal watercraft employs an engine cooling system in which its engine is cooled by the water from the water jet pump and thereafter, the water is discharged outside the watercraft, rather than a closed circulation type engine cooling system of automobile.
FIG. 6 is a schematic structure of the engine cooling system of the personal watercraft. In the engine cooling system, a water jet pump 107 is connected to an engine 104 through a pipe 150. A cooling water passage (water jacket) is formed in the engine 104. A filter 151 is provided in the pipe 150. The filter 151 serves to eliminate substances such as small stones and waterborne plants.
In the personal watercraft using this cooling system, a riding seat is openable/closable or otherwise removable. By opening or removing the riding seat, an opening formed in a deck is exposed. In maintenance and replacement of the filter 151, the filter 151 is accessible through the opening.
The cooling water passage formed in the engine 104 will now be described. The engine 104 is comprised of an engine body portion 120, an exhaust system 130. The engine body portion 120 is constituted by a cylinder block, a cylinder head, a crankcase, a crankshaft, pistons, and the like. The exhaust system 130 is constituted by an exhaust manifold, an exhaust pipe, an expansion chamber, a water muffler, an exhaust duct, and the like.
A water passage is formed in the cylinder block and the cylinder head. A water passage is also formed in the exhaust manifold, the exhaust pipe, and the expansion chamber. The cooling water passage of the engine 104 is comprised of these water passages.
The water is pumped into the pipe 150 by the water jet pump 107. The water flows through the filter 151 provided in the pipe 150 and then into the water passage of the exhaust system 130. Part of the water flowing into the water passage of the exhaust system 130 is diverged to flow and circulate through the water passage of the engine body portion 120 and is returned again to the water passage of the exhaust system 130.
An outlet of the cooling water passage of the engine 104 is connected to a pipe 156. A tip end of the pipe 156 extends to a pump room in the water jet pump 107. In brief, the water is sent into the cooling water passage of the engine by the water jet pump 107 and flows through the cooling water passage while exchanging heat, and the resulting water is sent into the pump room in the water jet pump 107 and discharged outside the watercraft.
A water-supply hole is provided in the expansion chamber. The cooling water is supplied to the inside of the expansion chamber through the water-supply hole and then sent into the water muffler, together with an exhaust gas.
In maintenance of the engine or the like of the personal watercraft, the personal watercraft is landed and the water in the cooling water passage of the engine is discharged.
However, in the personal watercraft having the water cooling system shown in FIG. 6, all the water in the cooling water passage of the engine 104 or the pipes 150, 156 is not discharged and is sometimes partially left. Even when all the water is discharged, the substances such as small stones or waterborne plants sometimes still remain in the cooling water passage or the pipes 150, 156. Further, especially after cruising on sea, salt remains adhered to the inner peripheral walls of the cooling water passage of the engine 104 or the pipes 150, 156.
As described above, the filter 151 is provided on the pipe 150 for eliminating the substances. For ease of maintenance of the filter 151, it is preferable that a portion of the pipe 150 where the filter 151 is provided is lifted relatively higher so that the filter 151 is readily accessible through the opening exposed by opening or removing the riding seat. Nonetheless, when the pipe 150 is partially higher than an inlet of the cooling water passage of the engine 104, the water between the higher portion and the inlet of the cooling water passage is difficult to discharge. The ease of discharge of the water is incompatible with the ease of maintenance of the filter 151. This limits layout of the pipe 150.
When the water-supply hole of the expansion chamber is clogged, the exhaust system 130 needs to be disassembled for cleaning the water-supply hole.
The present invention addresses the above-described condition, and an object of the present invention is to provide a personal watercraft having a water cooling system of an engine, which allows inside of a cooling water passage of an engine or a water passage connected to the cooling water passage of the engine to be sufficiently cleaned.
Another object of the present invention is to provide a personal watercraft that allows a water-supply hole of an expansion chamber to be easily inspected and cleaned.
According to the present invention, there is provided a personal watercraft comprising: a water jet pump; a cooling water passage of an engine; a first water passage from the water jet pump to the cooling water passage; a second water passage opened in a surface of a body of the watercraft and communicating with the first water passage; and an opening/closing means for opening/closing the second water passage, wherein a cooling water is forcibly sent to the first water passage by the water jet pump and led to the cooling water passage through the first water passage, the water flows through the cooling water passage while exchanging heat, and the resulting water is discharged outside the body of the watercraft.
In the personal watercraft so constituted, after the personal watercraft is landed, water in the cooling water passage is discharged from the second water passage by opening the second water passage. Further, a cleaning water can be forcibly supplied from the outside into the cooling water passage and the first water passage through the second water passage. Thus, the inside of the cooling water passage of the engine and the first water passage can be positively cleaned even in the case of using the water passage of ups and downs. Consequently, degree of freedom of layout of the first water passage is improved.
A first portion of the first water passage may be located higher than an inlet of the cooling water passage, and the second water passage may branch from a position of the first water passage between the first portion and the inlet of the cooling water passage.
When the first portion of the first passage is located higher than the inlet of the cooling water passage, the water in the first water passage between the first portion and the inlet of the cooling water passage is hardly discharged merely by landing the personal watercraft. However, in the above-mentioned structure, such water can be easily discharged from the second water passage. Further, by forcibly flowing the cleaning water into the first water passage through the second water passage, the cooling water between the first portion and inlet of the cooling water passage can be expelled.
In the personal watercraft, a filter may be provided in the first water passage, and the second water passage may branch from a position of the first water passage between the filter and an inlet of the cooling water passage.
When the filter is provided on the first water passage, the water in the first water passage between the filter and the inlet of the cooling water passage is hardly discharged merely by landing the personal watercraft. This is because the water between the filter and the inlet is less likely to flow back through the filter, and therefore is difficult to discharge. However, in the above-mentioned structure, such water is easily discharged through the second water passage. Besides, by forcibly flowing the cleaning water into the first water passage through the second water passage, the water between the filter and the inlet of the cooling water passage can be expelled.
A tip end of the second water passage may be opened in a rear end face of the body.
According to the present invention, there is further provided a personal watercraft comprising: an expansion chamber in an exhaust system of an engine; and a water muffler provided at a position downstream of the expansion chamber in the exhaust system of the engine, wherein the expansion chamber has a double-walled structure comprised of inner and outer walls between which water flows and is provided with a water-supply hole in the inner wall to allow water to be supplied into inside of the expansion chamber through the water-supply hole, an inspection hole is formed in the outer wall at a position corresponding to a position of the water-supply hole, and a cap member is removably attached to the inspection hole.
Since the inspection hole is formed in the outer wall of the double-walled structure of the expansion chamber at the position corresponding to the water-supply hole, the water-supply hole is readily accessible through the inspection hole by removing the cap member. Therefore, the inspection of the water-supply hole can be easily carried out and the water-supply hole can be easily cleaned.
The exhaust system may be provided with a temperature sensor located downstream of the water-supply hole in an exhaust gas flow path, for detecting temperature of an exhaust gas.
In the above-mentioned structure, the clogging in the water-supply hole can be quickly found by detecting that the temperature of the exhaust gas is higher than a proper temperature.
The above and further objects and features of the invention will be more fully be apparent from the following detailed description with accompanying drawings.